if an error is thrown by a loader(), we only log it to the console, but silently let the canvas run forward, which may lead to other runtime errors that are misleading

[balazsbajorics]

steps to reproduce: open the hydrogen test project, put a throw new Error('hello') in any of the loaders, and witness as the error is logged to the console, but the canvas is still rendering.

fix: the error message should show up as a big red canvas runtime error, with our usual source code snippet handling etc

[seanparsons]

@balazsbajorics I added one of these to a loader and it worked fine:

Maybe it only breaks for a certain kind?